Organic electroluminescent display device and method of fabricating the same

ABSTRACT

A method for fabricating an organic electroluminescent display device including the steps of preparing first and second substrates, forming an organic electroluminescent display on the first substrate, forming a first etching mask film on an upper surface of the second substrate, forming a second etching mask film on a lower surface of the second substrate, performing a first etching process on the upper surface of the second substrate, forming a third etching mask film on an etched portion of the second surface of the glass substrate, performing a second etching process on the upper surface of the second substrate to form a plurality of grooves on the upper surface of the second substrate, removing the first and second etching mask films, the second etching film remaining on the etched portion of the second surface of the glass substrate, and encapsulating the organic electroluminescent display between the first and second substrates.

The present application claims the benefit of Korean Patent ApplicationNo. 10-2009-0065190 filed in Korea on Jul. 17, 2009, which is herebyincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic electroluminescent display(ELD) device, and more particularly, to an organic electroluminescentdisplay device where deterioration due to bending and protrusion isprevented and a method of fabricating the same.

2. Discussion of the Related Art

Among flat panel displays (FPDs), organic ELD devices have been ofparticular interest in research and development because they have highbrightness and low driving voltage. For example, since the organic ELDdevices are driven with a low voltage of between DC 5V and DC 15V, adriving circuit may be easily designed and fabricated. In addition,since organic ELD devices are an emissive type, organic ELD devices havea high contrast ratio and a thin profile. Also, organic ELD devices candisplay images without viewing angle limitations. Further, since organicELD devices have a short response time of several microseconds (μs ),the organic ELD devices have a stable operation property at a lowtemperature and an advantage in displaying moving images.

Organic ELD devices may be classified into a passive matrix type and anactive matrix type according to existence of a switching element. In apassive matrix type organic ELD device where a scan line and a signalline that cross each other to define a pixel region are disposed in amatrix without a switching element, the light of each pixel region mayhave an instant brightness obtained by multiplying a required averagebrightness and the number of the scan line since each pixel region emitslight only while the corresponding scan line is selected.

In an active matrix type organic ELD device where a scan line and asignal line that cross each other to define a pixel region are disposedin a matrix and a thin film transistor (TFT) as a switching element anda storage capacitor are disposed in each pixel region, the light of eachpixel region may have an instant brightness corresponding to a requiredaverage brightness since a voltage applied to each pixel region ismaintained during a frame due to the TFT and the storage capacitor. As aresult, the active matrix organic ELD device may have the requiredaverage brightness even with a relatively low voltage as compared withthe passive matrix organic ELD device. Accordingly, the active matrixorganic ELD device has been widely used due to the advantages of lowpower consumption, high resolution, and large size.

FIG. 1 is a circuit diagram showing an active matrix type organic ELDdevice according to the related art. In FIG. 1, a pixel region P of anactive matrix type organic ELD device includes a switching thin filmtransistor (STr), a driving thin film transistor (DTr), a storagecapacitor StgC, and an organic electroluminescent diode E. A gate lineGL is disposed along a first direction, and a data line DL is disposedalong a second direction crossing the first direction. The gate line GLand the data line DL cross each other to define the pixel region P. Apower line PL is parallel to and spaced apart from one of the gate lineGL and the data line DL. The switching TFT STr is connected to the gateline GL and the data line DL, and the driving TFT DTr is electricallyconnected to the switching TFT STr. In addition, the driving TFT DTr iselectrically connected to the organic electroluminescent diode E and thepower line PL. For example, a first electrode of the organicelectroluminescent diode E may be connected to a drain electrode of thedriving TFT DTr, and a source voltage of the power line PL istransmitted to the organic electroluminescent diode E through thedriving TFT DTr. The storage capacitor StgC is formed between a gateelectrode and a source electrode of the driving TFT DTr.

When a gate signal is applied to the gate line GL, the switching TFT STris turned on and a data signal of the data line DL is applied to thegate electrode of the driving TFT DTr. As a result, the driving TFT DTris turned on and light is emitted from the organic electroluminescentdiode E. The grey level of the light emitted from the organicelectroluminescent diode E is determined according to the intensity of acurrent flowing from the power line PL to the organic electroluminescentdiode E through the driving TFT DTr. Since the storage capacitor StgCkeeps the voltage of the gate electrode of the driving TFT DTr constantwhile the switching TFT STr is turned off, the constant current flowsthrough the organic electroluminescent diode E during a frame even whenthe switching TFT STr is turned off

FIG. 2 is a cross-sectional view showing an organic electroluminescentdisplay device according to the related art. In FIG. 2, an organic ELDdevice includes first and second substrates 3 and 31 facing each other.The first substrate 3 includes glass and the second substrate 31 is usedfor encapsulation. A boundary portion of the first and second substrates3 and 31 is sealed with a seal pattern 40. A driving thin filmtransistor DTr and a first electrode 12 are formed in each pixel regionP on the first substrate 3, and the first electrode 12 is connected tothe driving TFT DTr. An organic luminescent layer 14 is formed on thefirst electrode 12, and a second electrode 16 is formed on the organicluminescent layer 14. The organic luminescent layer 14 includes red,green, and blue emitting material patterns 14 a, 14 b and 14 c emittingred, green, and blue lights, respectively, and the second electrode 16is formed on the red, green, and blue emitting material patterns 14 a,14 b and 14 c. An electric field generated between the first and secondelectrodes 12 and 16 is applied to the organic luminescent layer 14, andthe first electrode 12, and the second electrode 16 constitute anorganic electroluminescent diode E.

The first and second substrates 3 and 31 are attached to each other bythe seal pattern 40, and the second electrode 16 over the firstsubstrate 3 is spaced apart from the second substrate 31. The secondsubstrate 31 includes a groove GR on an inner surface thereof, and anabsorbent material 32 such as barium oxide (BaO) or calcium oxide (CaO)is formed in the groove GR to prevent moisture penetration from theexterior. Since the organic luminescent layer 14 deteriorates fromexposure to oxygen or moisture, the first substrate 3 including theorganic luminescent layer 14 is encapsulated by the second substrate 31including the absorbent material 32 so that penetration of oxygen ormoisture can be prevented.

The absorbent material 32 has a thickness t within a range of about 150μm to about 250 μm, and the first and second substrates 3 and 31 have agap distance within a range of about 6 μm to about 12 μm using a glassfiber (not shown) or a spacer (not shown). To keep the gap distancewithin a range of about 6 μm to about 12 μm, the groove GR having adepth greater than the thickness of the absorbent material 32 is formedin the second substrate 31 and the absorbent material 32 is formed inthe groove GR.

When the first and second substrates 3 and 31 are formed to be spacedapart from each other by a gap distance greater than about 150 μm usinga thick glass fiber or a thick spacer, the waste of material increasesand the thickness of the organic ELD device increases. In addition,since the thick glass fiber or the thick spacer is vulnerable toexternal impact, the reliability of the organic ELD device is reduced.Further, since a thickness of the seal pattern 40 increases, an areaexposed to the exterior increases and penetration of oxygen or moistureincreases. Accordingly, the groove GR is formed in the second substrate31 and the absorbent material 32 is formed in the groove GR.

However, since the groove GR is formed in the second substrate 31, thethickness of the second substrate 31 corresponding to the groove GR isreduced and the second substrate 31 having a reduced thickness isvulnerable to external impact. For example, the second substrate 31 maybe broken or cracked during one of the steps of forming the absorbentmaterial 32 in the groove GR, attaching the first and second substrates3 and 31, or transferring the second substrate 31. In addition, thegroove GR is formed to correspond to a display area of the secondsubstrate 31 and the absorbent material 32 is formed in the groove GR.As a result, light of the organic electroluminescent diode E cannot beemitted through the second substrate 32 and the organic ELD devicecannot be applied to an upper emission type.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an organicelectroluminescent display device and a method of fabricating the samethat substantially obviate one or more of the problems due tolimitations and disadvantages of the related art.

An object of the present invention is to provide an organic ELD deviceincluding an encapsulation substrate and a method of fabricating theorganic ELD device.

Another object of the present invention is to provide an organic ELDdevice applicable to an upper emission type and a method of fabricatingthe organic ELD device.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein, theorganic electroluminescent display device and method of fabricating thesame includes a method for fabricating an organic electroluminescentdisplay device including the steps of preparing first and secondsubstrates, forming an organic electroluminescent display on the firstsubstrate, forming a first etching mask film on an upper surface of thesecond substrate, forming a second etching mask film on a lower surfaceof the second substrate, performing a first etching process on the uppersurface of the second substrate, forming a third etching mask film on anetched portion of the second surface of the glass substrate, performinga second etching process on the upper surface of the second substrate toform a plurality of grooves on the upper surface of the secondsubstrate, removing the first and second etching mask films, the secondetching film remaining on the etched portion of the second surface ofthe glass substrate, and encapsulating the organic electroluminescentdisplay between the first and second substrates.

In another aspect, the organic electroluminescent display device andmethod of fabricating the same includes a method for fabricating anorganic electroluminescent display device including the steps ofpreparing first and second substrates, forming an organicelectroluminescent display on the first substrate, forming a firstetching mask film on an upper surface of the second substrate, forming asecond etching mask film on a lower surface of the second substrate,performing a first etching process on the upper surface of the secondsubstrate, forming a third etching mask film on an etched portion of thesecond surface of the glass substrate, performing a second etchingprocess on the upper surface of the second substrate to form a pluralityof grooves on the upper surface of the second substrate, removing thefirst, second, and third etching mask films, forming a first insulatingmaterial layer on the entire upper surface of the second substrate,removing end portions of the first insulating layer, the firstinsulating layer remaining on the etched portion of the second surfaceof the glass substrate, and encapsulating the organic electroluminescentdisplay between the first and second substrates.

In another aspect, the organic electroluminescent display device andmethod of fabricating the same includes a method of fabricating anorganic electroluminescent display device, including the steps offorming an organic electroluminescent diode on a first substrateincluding a display area and a non-display area surrounding the displayarea, forming a first etching mask film on first and second surfaces ofa second substrate including a first region corresponding to thenon-display area, a second region corresponding to the display area anda third region between the first and second region, the first etchingmask film disposed in the first region of the first surface and in thefirst, second and third regions of the second surface, etching thesecond substrate using the first etching mask film as an etching mask sothat the second substrate of the first region has a first thickness andthe second substrate of the second and third regions has a secondthickness smaller than the first thickness, forming a second etchingmask film on the first surface, the second etching mask film disposed inthe second region of the first surface and in portions of the thirdregion of the first surface, and other portions of the third region ofthe first surface exposed through the second etching mask film, etchingthe second substrate using the first and second etching mask films toform a plurality of grooves corresponding to the other portions of thethird region, the second substrate corresponding to the plurality ofgrooves having a third thickness smaller than the second thickness,removing the first etching mask film on the first and second surfaces,forming an absorbent material in the plurality of grooves, and attachingthe first and second substrates such that the organic electroluminescentdiode faces the first surface.

In another aspect, the organic electroluminescent display device andmethod of fabricating the same includes an organic electroluminescentdisplay device including a first substrate including a display area anda non-display area surrounding the display area, an organicelectroluminescent diode in the display area on the first substrate, asecond substrate facing and spaced apart from the first substrate, thesecond substrate including a first region corresponding to thenon-display area, a second region corresponding to the display area anda third region between the first and second region, wherein the secondsubstrate includes a plurality of grooves in the third region, andwherein the second substrate has a first thickness in the first region,a second thickness smaller than the first thickness in the second regionand a third thickness smaller than the second thickness in a portion ofthe third region where the plurality of grooves are formed, a protectionlayer in the second region on the second substrate, and a seal patternin the first region between the first and second substrates.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is a circuit diagram showing an active matrix type organic ELDdevice according to the related art;

FIG. 2 is a cross-sectional view showing an organic ELD device accordingto the related art;

FIG. 3 is a plane view showing an organic ELD device according to anexemplary first embodiment of the present invention;

FIG. 4 is a cross-sectional view taken along a line IV-IV of FIG. 3;

FIG. 5 is a cross-sectional view showing bending of a second substrateof an organic ELD device according to an exemplary first embodiment ofthe present invention;

FIG. 6 is a plane view showing an organic ELD device according to anexemplary second embodiment of the present invention;

FIG. 7A is a cross-sectional view taken along a line VII-VII of FIG. 6;

FIG. 7B is a cross-sectional view showing bending of a second substrateof an organic ELD device according to an exemplary second embodiment ofthe present invention;

FIG. 8A is a cross-sectional view showing an organic ELD deviceaccording to an exemplary third embodiment of the present invention;

FIG. 8B is a cross-sectional view showing bending of a second substrateof an organic ELD device according to an exemplary third embodiment ofthe present invention;

FIGS. 9A to 9F are cross-sectional views showing a method of fabricatingan organic ELD device according to an exemplary fourth embodiment of thepresent invention; and

FIGS. 10A to 10E are cross-sectional views showing a method offabricating an organic ELD device according to an exemplary fifthembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments,examples of which are illustrated in the accompanying drawings.

FIG. 3 is a plane view showing an organic electroluminescent displaydevice according to an exemplary first embodiment of the presentinvention, and FIG. 4 is a cross-sectional view taken along a line IV-IVof FIG. 3.

In FIGS. 3 and 4, an organic ELD device 100 includes a first substrate110 having a switching TFT (not shown), a driving thin film transistor(TFT) DTr and an organic electroluminescent diode E, and a secondsubstrate 170 facing the first substrate 110. The second substrate 170is used for encapsulating the first substrate 110. The first substrate110 includes a display area DA and a non-display area NA surrounding thedisplay area DA. A plurality of gate lines (not shown), a plurality ofdata lines, and a plurality of power lines (not shown) are formed in thedisplay area DA on the first substrate 110. The plurality of gate linescross the plurality of data lines to define a plurality of pixel regionsP, and the plurality of power lines are spaced apart from the pluralityof gate lines or the plurality of data lines. In addition, the switchingTFT connected to the gate and data line, the driving TFT DTr connectedto the switching TFT STr, and the power line are formed in each pixelregion P. A passivation layer 130 having a flat top surface is formed onthe switching TFT STr and the driving TFT DTr, and a first electrode 150is formed on the passivation layer 130 in each pixel region P. Thepassivation layer 130 includes a contact hole 132 exposing an electrodeof the driving TFT DTr, and the first electrode 150 is connected to theelectrode of the driving TFT DTr through the contact hole 132.

Further, a buffer pattern 152 is formed on the first electrode 150 at aboundary portion of each pixel region P. The buffer pattern 152 coversand overlaps edge portions of the first electrode 150. An organicluminescent layer 155 is formed on the first electrode 150 inside thebuffer pattern 152, and a second electrode 160 is formed on the organicluminescent layer 155. The second electrode 160 may be formed in thewhole display area DA as a single body. The first electrode 150, theorganic luminescent layer 155, and the second electrode 160 constitutethe organic electroluminescent diode E.

Elements such as link lines (not shown) and pads for connection to anexternal driving circuit (not shown) are formed in the non-display areaNA of the first substrate 110. Although the passivation layer 130 isremoved in the non-display area NA for improving contact property inFIGS. 3 and 4, the passivation layer 130 may remain in the non-displayarea NA for protecting the elements such as the link lines.

The second substrate 170 includes a first region A1 corresponding to thenon-display area NA, a second region A2 surrounded by the first regionA1 and a third region A3 between the first and second regions A1 and A2.The second substrate 170 may include a transparent glass. The firstregion A1 of the second substrate 170 that is not etched may have afirst thickness t1, and the second region A2 of the second substrate 170that is etched once may have a second thickness t2 smaller than thefirst thickness t1. A plurality of grooves GR is formed in the thirdregion A3 of the second substrate 170. In addition, the third region A3of the second substrate 170 corresponding to the plurality of grooves GRmay have a third thickness t3 smaller than the second thickness t2 andthe other portions of the third region A3 may have the second thicknesst2. The plurality of grooves GR may be uniformly spaced apart from eachother by a predetermined distance. An absorbent material 180 such asbarium oxide (BaO) or calcium oxide (CaO) are formed in each of theplurality of grooves GR of the third region A3 of the second substrate170.

The first and second substrates 110 and 170 are attached with a sealpattern 190 such that the display area DA of the first substrate 110faces the second region A2 of the second substrate 170. The seal pattern190 is formed between the first and second substrates 110 and 170 in thefirst region A1.

In the organic electroluminescent display device 100 according to thefirst exemplary embodiment of the present invention, deterioration suchas breaks or cracks due to external impact are prevented since thesecond substrate 170 has the second thickness t2 greater than the thirdthickness t3 in the second region A2 corresponding to the display areaDA. Further, the second substrate 170 has the third thickness t3 in theplurality of grooves GR of the third region A3. Deterioration due to theexternal impact is reduced since the plurality grooves GR are disposedto be spaced apart from each other and portions having the first orsecond thickness t1 or t2 surround each of the plurality of grooves GR.

As a size of an organic ELD device increases, a display area of theorganic ELD device increases. In addition, as the display area of theorganic eELD device increases, deterioration due to the bending of asecond substrate may increase.

FIG. 5 is a cross-sectional view showing bending of a second substrateof an organic ELD device according to an exemplary first embodiment ofthe present invention.

In FIG. 5, a second substrate 170 having a relatively large size is benteven by a relatively small external force. Although a gap distancebetween the first substrate 110 in the display area DA and the secondsubstrate 170 in the second region A2 is several micrometers, the secondsubstrate 170 contacts the second electrode 160 of the first substrate110 due to the bending of the second substrate 170. When the secondsubstrate 170 has a flat inner surface, the organic ELD device 100 isnot deteriorated by the bending of the second substrate 170 because thesecond electrode 160 is formed of a metallic material. However, aprotrusion having a height of about 1 μm to about 3 μm may be formed onthe inner surface of the second substrate 170 of the second region A2since the second substrate 170 of the second and third regions A2 and A3is etched with an etching solution such as hydrofluoric acid (HF) tohave the second and third thicknesses t2 and t3, respectively. When thesecond substrate 170 of the second region A2 is bent to contact thesecond electrode 160 of the first substrate 110, the second electrode160 may be broken by the protrusion, or the first and second electrodes150 and 160 may be electrically connected by the protrusion. As aresult, the display quality of the organic ELD device 100 isdeteriorated. Although deterioration due to contact of the protrusion isprevented by further etching the second substrate 170 of the secondregion A2, the second substrate 170 of the second region A2 may beeasily cracked or broken due to a reduced thickness.

FIG. 6 is a plane view showing an organic ELD device according to anexemplary second embodiment of the present invention. FIG. 7A is across-sectional view taken along a line VII-VII of FIG. 6 and FIG. 7B isa cross-sectional view showing bending of a second substrate of anorganic ELD device according to an exemplary second embodiment of thepresent invention.

In FIGS. 6, 7A, and 7B, an organic ELD device 200 includes a firstsubstrate 210 having a switching TFT (not shown), a driving thin filmtransistor (TFT) DTr, an organic electroluminescent diode E, and asecond substrate 270 facing the first substrate 210. The secondsubstrate 270 is used for encapsulating the first substrate 210. Thefirst substrate 210 includes a display area DA and a non-display area NAsurrounding the display area DA. A plurality of gate lines (not shown),a plurality of data lines, and a plurality of power lines (not shown)are formed in the display area DA on the first substrate 210. Theplurality of gate lines cross the plurality of data lines to define aplurality of pixel regions P, and the plurality of power lines arespaced apart from the plurality of gate lines or the plurality of datalines. In addition, the switching TFT connected to the gate and dataline, the driving TFT DTr connected to the switching TFT STr, and thepower line are formed in each pixel region P. A passivation layer 230having a flat top surface is formed on the switching TFT STr and thedriving TFT DTr, and a first electrode 250 is formed on the passivationlayer 230 in each pixel region P. The passivation layer 230 includes acontact hole 232 exposing an electrode of the driving TFT DTr, and thefirst electrode 250 is connected to the electrode of the driving TFT DTrthrough the contact hole 232.

Further, a buffer pattern 252 is formed on the first electrode 250 at aboundary portion of each pixel region P. The buffer pattern 252 coversand overlaps edge portions of the first electrode 250. An organicluminescent layer 255 is formed on the first electrode 250 inside thebuffer pattern 252, and a second electrode 260 is formed on the organicluminescent layer 255. The second electrode 260 may be formed in thewhole display area DA as a single body. The first electrode 250, theorganic luminescent layer 255, and the second electrode 260 constitutethe organic electroluminescent diode E.

Elements such as link lines (not shown) and pads for connection to anexternal driving circuit (not shown) are formed in the non-display areaNA of the first substrate 210. Although the passivation layer 230 isremoved in the non-display area NA for improving contact property inFIGS. 6, 7A and 7B, the passivation layer 230 may remain in thenon-display area NA for protecting the elements such as the link lines.

The second substrate 270 includes a first region A1 corresponding to thenon-display area NA, a second region A2 surrounded by the first regionA1, and a third region A3 between the first and second regions A1 andA2. The second substrate 270 may include a transparent glass. The firstregion A1 of the second substrate 270 that is not etched may have afirst thickness t1, and the second region A2 of the second substrate 270that is etched once may have a second thickness t2 smaller than thefirst thickness t1. A plurality of grooves GR is formed in the thirdregion A3 of the second substrate 270. In addition, the third region A3of the second substrate 270 corresponding to the plurality of grooves GRmay have a third thickness t3 smaller than the second thickness t2, andthe other portions of the third region A3 may have the second thicknesst2. The plurality of grooves GR may be uniformly spaced apart from eachother by a predetermined distance. An absorbent material 280 such asbarium oxide (BaO) or calcium oxide (CaO) are formed in each of theplurality of grooves GR of the third region A3 of the second substrate270.

The first and second substrates 210 and 270 are attached with a sealpattern 290 such that the display area DA of the first substrate 210faces the second region A2 of the second substrate 270. The seal pattern290 is formed between the first and second substrates 210 and 270 in thefirst region A1.

In the organic ELD device 200 according to the exemplary secondembodiment of the present invention, a protection layer 273 is formed inthe second region A2 on an inner surface of the second substrate 270.The protection layer 273 is used as an etching mask film for the secondregion A2 while the second substrate 270 of the third region A3 isetched for forming the plurality of grooves GR. Since the etching maskfilm for forming the plurality of grooves GR in the second substrate 270is used as the protection layer 273, the protection layer 273 is formedwithout an additional photolithographic process including deposition orcoating.

The protection layer 273 includes a transparent material havingexcellent elasticity and excellent surface roughness. For example, theprotection layer 273 may include one of acryl, polycarbonate, andpoly-ethylene-terephthalate (PET). Although not shown in FIG. 7A, anadhesive may be formed between the second substrate 270 of the secondregion A2 and the protection layer 273.

Since the protection layer 273 is formed on the inner surface of thesecond substrate 270 in the second region A2, a protrusion formed fromthe etching step for the second region A2 is covered with the protectionlayer 273, and the inner surface of the second substrate 270 in thesecond region A2 is planarized by the protection layer 273. As a result,deterioration of the second electrode 260 due to the protrusion isprevented even when the second substrate 270 is bent by an externalforce. In addition, since the protection layer 273 has excellentelasticity, deterioration of the second electrode 260 is reduced evenwhen the protection layer 273 contacts the second electrode 260.

FIG. 8A is a cross-sectional view showing an organic ELD deviceaccording to an exemplary third embodiment of the present invention, andFIG. 8B is a cross-sectional view showing bending of a second substrateof an organic ELD device according to an exemplary third embodiment ofthe present invention.

In FIGS. 8A and 8B, an organic ELD device 300 includes a first substrate310 having a switching TFT (not shown), a driving thin film transistor(TFT) DTr, an organic electroluminescent diode E, and a second substrate370 facing the first substrate 310. The second substrate 370 is used forencapsulating the first substrate 310. The first substrate 310 includesa display area DA and a non-display area NA surrounding the display areaDA. A plurality of gate lines (not shown), a plurality of data lines,and a plurality of power lines (not shown) are formed in the displayarea DA on the first substrate 310. The plurality of gate lines crossthe plurality of data lines to define a plurality of pixel regions P,and the plurality of power lines are spaced apart from the plurality ofgate lines or the plurality of data lines. In addition, the switchingTFT connected to the gate and data line, and the driving TFT DTrconnected to the switching TFT STr, and the power line are formed ineach pixel region P. A passivation layer 330 having a flat top surfaceis formed on the switching TFT and the driving TFT DTr, and a firstelectrode 350 is formed on the passivation layer 330 in each pixelregion P. The passivation layer 330 includes a contact hole 332 exposingan electrode of the driving TFT DTr, and the first electrode 350 isconnected to the electrode of the driving TFT DTr through the contacthole 332.

Further, a buffer pattern 352 is formed on the first electrode 350 at aboundary portion of each pixel region P. The buffer pattern 352 coversand overlaps edge portions of the first electrode 350. An organicluminescent layer 355 is formed on the first electrode 350 inside thebuffer pattern 352, and a second electrode 360 is formed on the organicluminescent layer 355. The second electrode 360 may be formed in thewhole display area DA as a single body. The first electrode 350, theorganic luminescent layer 355, and the second electrode 360 constitutethe organic electroluminescent diode E.

The organic luminescent layer 355 may be formed through a nozzle coatingmethod or an inkjet method. Alternatively, the organic luminescent layer355 may be formed through a thermal evaporation method using a shadowmask. Although not shown in FIGS. 8A and 8B, a plurality of spacers eachhaving a bar shape may be formed on the buffer pattern 352 when theorganic luminescent layer 355 is formed using the shadow mask. While theorganic luminescent layer 355 is formed through the thermal evaporationmethod, the plurality of spacers support the shadow mask to preventwarpage of the shadow mask.

Elements such as link lines (not shown) and pads for connection to anexternal driving circuit (not shown) are formed in the non-display areaNA of the first substrate 310. Although the passivation layer 330 isremoved in the non-display area NA for improving contact property inFIGS. 8A and 8B, the passivation layer 330 may remain in the non-displayarea NA for protecting the elements such as the link lines.

The second substrate 370 includes a first region A1 corresponding to thenon-display area NA, a second region A2 surrounded by the first regionA1, and a third region A3 between the first and second regions A1 andA2. The second substrate 370 may include a transparent glass. The firstregion A1 of the second substrate 370 that is not etched may have afirst thickness t1, and the second region A2 of the second substrate 370that is etched once may have a second thickness t2 smaller than thefirst thickness t1. A plurality of grooves GR is formed in the thirdregion A3 of the second substrate 370. In addition, the third region A3of the second substrate 370 corresponding to the plurality of grooves GRmay have a third thickness t3 smaller than the second thickness t2 andthe other portions of the third region A3 may have the second thicknesst2. The plurality of grooves GR may be uniformly spaced apart from eachother by a predetermined distance. An absorbent material 380 such asbarium oxide (BaO) or calcium oxide (CaO) are formed in each of theplurality of grooves GR of the third region A3 of the second substrate370.

The first and second substrates 310 and 370 are attached with a sealpattern 390 such that the display area DA of the first substrate 310faces the second region A2 of the second substrate 370. The seal pattern390 is formed between the first and second substrates 310 and 370 in thefirst region A1.

In the organic ELD device 300 according to an exemplary third embodimentof the present invention, a protection layer 373 is formed in the secondregion A2 on an inner surface of the second substrate 370, and aplurality of protection patterns 375 each having a bar shape are formedon the protection layer 373. One of the protection layer 373 and theplurality of protection patterns 375 may include one of an organicinsulating material, such as photo acryl and benzocyclobutene (BCB), andan inorganic insulating material, such as silicon nitride (SiNx) andsilicon oxide (SiO₂). The protection layer 373 may have a thickness ofabout 2 μm to about 3 μm and each of the plurality of protectionpatterns 375 may have a height of about 1 μm to about 2μm. In addition,the plurality of protection patterns 375 may be parallel to and spacedapart from each other. When the plurality of spacers are formed on thebuffer pattern 352 over the first substrate 310, the plurality ofprotection patterns 375 may be formed to be perpendicular to theplurality of spacers. Alternatively, the protection layer 373, includingone of an organic or inorganic insulating material, is formed on theinner surface of the second substrate 370, and the plurality ofprotection patterns 375 may be omitted.

Since the protection layer 373 is formed on the inner surface of thesecond substrate 370 in the second region A2, a protrusion formed fromthe etching step for the second region A2 is covered with the protectionlayer 373, and the inner surface of the second substrate 370 in thesecond region A2 is planarized by the protection layer 373. As a result,deterioration of the second electrode 360 due to the protrusion isprevented even when the second substrate 370 is bent by an externalforce. In addition, since the protection layer 373 has excellentelasticity, deterioration of the second electrode 360 is reduced evenwhen the protection layer 373 contacts the second electrode 360.

Further, when the plurality of protection patterns 375 are formed on theprotection layer 373, deterioration due to a protrusion having a heightof about 4 μm to about 5μm is prevented by the plurality of protectionpatterns 375. Since the protrusion is disposed between the adjacent twoprotection patterns 375 or covered with one of the plurality ofprotection patterns 375, the plurality of protection patterns 375contact the second electrode 360 when the second substrate 370 is bentby an external force. As a result, breakage of the second electrode 360and electric shortage of the first and second electrodes 310 and 360 areprevented.

Moreover, in an organic ELD device where the plurality of spacers areformed on the buffer pattern 352 over the first substrate 310 and theplurality of protection patterns 375 perpendicular to the plurality ofspacers are formed on the second substrate 360, the plurality ofprotection patterns 375 contact the plurality of spacers when the secondsubstrate 360 is bent by an external force. As a result, contact area isminimized and deterioration due to the protrusion is more stablyprevented by the height of each spacer.

FIGS. 9A to 9F are cross-sectional views showing a method of fabricatingan organic ELD device according to an exemplary fourth embodiment of thepresent invention.

In FIG. 9A, after a first etching mask film 271 is formed on each offirst and second surfaces of a substrate 270, having first, second, andthird regions A1, A2, and A3, portions of the first etching mask film271 corresponding to the second and third regions A2 and A3 are removedfrom the first surface of the second substrate 270. As a result, thefirst etching mask film 271 is formed on the first surface of the secondsubstrate 270 corresponding to the first region A1 and the first surfaceof the second substrate 270 corresponding to the second and thirdregions A2 and A3 are exposed through the first etching mask film 271.In addition, the first etching mask film 271 is formed on the wholesecond surface of the second substrate 270.

The second substrate 270 may be formed of a transparent glass and have afirst thickness t1. Further, the first etching mask film 271 may beformed of a transparent material such as acryl, polycarbonate, andpoly-ethylene-terephthalate (PET) through a transcribing method, and anadhesive (not shown) may be formed between the first etching mask film271 and the second substrate 270. The first and second regions A1 and A2correspond to center and boundary portions, respectively, of the secondsubstrate 270, and the third region A3 is disposed between the first andsecond regions A1 and A2.

In FIG. 9B, a first etching step using the first etching mask film 271as an etching mask is performed for the second substrate 270. Forexample, the second substrate 270 may be etched with an etching solutionsuch as hydrofluoric acid (HF) through a spraying method or a dippingmethod. As a result, the second substrate 270 exposed through the firstetching mask film 271 is etched, and the second substrate 270corresponding to the second and third regions A2 and A3 has a secondthickness t2 smaller than the first thickness t1. After the firstetching step, a plurality of protrusions may be formed on the firstsurface of the second substrate 270 due to partial etching difference.

In FIG. 9C, a second etching mask film 272 is formed on the firstsurface of the second substrate 270 corresponding to the second regionA2 and portions of the third region A3 where a plurality of grooves GR(of FIG. 9D) are not formed in a subsequent process. For example, thesecond etching mask film 272 may be attached to the first surface usingan adhesive. As a result, the first etching mask film 271 is formed onthe first surface of the second substrate 270 corresponding to the firstregion A1. The first etching mask film 271 is formed on the whole secondsurface of the second substrate 270. Also, the second etching mask 272is formed on the first surface of the second substrate 270 correspondingto the second region A2 and the portions of the third region A3 wherethe plurality of grooves GR are not formed in a subsequent process.Meanwhile, the first surface of the second substrate 270 correspondingto the portions of the third region A3 where the plurality of grooves GRare formed in a subsequent process is exposed through the first andsecond etching mask films 271 and 272.

Alternatively, the first etching mask film 271 on the first surface ofthe second substrate 270 corresponding to the first region A1 may beremoved after the first etching step and the second etching mask film272 may be formed on the first surface of the second substrate 270corresponding to the first region A1.

In FIG. 9D, a second etching step using the first and second etchingmask films 271 and 272 as an etching mask is performed for the secondsubstrate 270. For example, the second substrate 270 may be etched withan etching solution such as hydrofluoric acid (HF) through a sprayingmethod or a dipping method. As a result, the second substrate 270exposed through the first and second etching mask films 271 and 272 isetched to form the plurality of grooves GR in the third region A3, andthe second substrate 270 corresponding to the plurality of grooves GR inthe third region A3 has a third thickness t3 smaller than the secondthickness t2.

In FIG. 9E, the first etching mask film 271 is removed from the firstsurface of the second substrate 270 corresponding to the first region A1and the second surface of the second substrate 270, and the secondetching mask film 272 remains on the first surface of the secondsubstrate 270 corresponding to the second region A2 and the portions ofthe third region A3 where the plurality of grooves GR is not formed.Accordingly, the second substrate 270 has the first thickness t1 at thefirst region A1, the second thickness t2 at the second region A2 and theportions of the third region A3 where the plurality of grooves GR arenot formed, and the third thickness t3 at the plurality of grooves GR ofthe third region A3. In addition, the second etching mask film 272 inthe second region A2 remains to become the protection layer 273 (ofFIGS. 6, 7A, and 7B) covering the plurality of protrusions andpreventing deterioration due to the plurality of protrusions.

In FIG. 9F, an absorbent material 280 is formed in the plurality ofgrooves GR. Referring to the organic ELD device 100 (of FIGS. 3 and 4)according to the exemplary first embodiment of the present invention,the second etching mask film may be removed and the absorbent materialmay be formed in the plurality of grooves after the second substrate 170(of FIGS. 3 and 4) is fabricated through the steps of FIGS. 9A to 9E.

FIGS. 10A to 10E are cross-sectional views showing a method offabricating an organic electroluminescent display device according to anexemplary fifth embodiment of the present invention.

In FIG. 10A, a second substrate 370 having first, second, and thirdthicknesses t1, t2, and t3 is fabricated through steps similar to thoseshown in FIGS. 9A to 9E. The first thickness t1 corresponds to a firstregion A1, and the second thickness t2 corresponds to a second region A2and portions of a third region A3 where a plurality of grooves GR arenot formed. In addition, the third thickness t3 corresponds to theplurality of grooves GR. A first etching mask film 371 is formed on afirst surface of the second substrate 370 in the first region A1 and awhole second surface of the second substrate 370, and a second etchingmask film 372 is formed on the first surface of the second substrate 370in the second region A2. A plurality of protrusions on the first surfaceof the second substrate 370 in the second region A2 are covered with thesecond etching mask film 372.

In FIG. 10B, the first and second etching mask films 371 and 372 areremoved from the second substrate 370. As a result, the first surfaceand the second surface including the plurality of protrusions of thesecond substrate 370 are exposed.

In FIG. 10C, a first insulating material layer 377 is formed on thewhole first surface of the second substrate 370 by coating an organicinsulating material or depositing an inorganic insulating material.

In FIG. 10D, the first insulating material layer 377 is patterned toform a protection layer 373 on the first surface of the second substrate370 in the second region A2. For example, the first insulating materiallayer 377 corresponding to the first and third regions A1 and A3 may beremoved, and the first insulating material layer 377 corresponding tothe second region A2 may remain. As a result, the protection layer 373covers the plurality of protrusions of the second substrate 370.

In FIG. 10E, after a second insulating material layer (not shown) isformed on the protection layer 373, the second insulating material ispatterned to form a plurality of protection patterns 375 on theprotection layer 373. For example, the second insulating material layermay be formed by coating an organic insulating material or depositing aninorganic insulating material. In addition, each of the plurality ofprotection patterns 375 may have a bar shape, and the plurality ofprotection patterns 375 may be parallel to and spaced apart from eachother. After the plurality of protection patterns 375 are formed, anabsorbent material 380 is formed in the plurality of grooves GR in thethird region A3.

Alternatively, the plurality of protection patterns 375 may be omitted.In yet another alternative, the protection layer 373 and the pluralityof protection patterns 375 may be formed through a single mask processincluding a coating step of an insulating material, an exposure stepusing a photo mask having a blocking area, a half-transmissive area, anda transmissive area and a patterning step.

Moreover, first substrates of organic ELD devices according to first tothird embodiments of the present invention may be fabricated through thesame method. For example, a gate line and a data line with an interposedinsulating layer are formed on a first substrate 110 (of FIG. 4). Apower line parallel to and spaced apart from one of the gate line andthe data line is formed on the first substrate 110. In addition, aswitching thin film transistor (TFT) connected to the gate line and thedata line and a driving TFT DTr (of FIG. 4) connected to the switchingTFT and the power line are formed on the first substrate 110. Next, apassivation layer 130 is formed on the switching TFT and the driving TFTDTr. The passivation layer 130 includes a contact hole 132 (of FIG. 4)exposing an electrode of the driving TFT DTr.

Next, a first electrode 150 is formed on the passivation layer 130. Thefirst electrode 150 is connected to the electrode of the driving TFT DTrthrough the contact hole 132 and disposed in each pixel region P (ofFIG. 4). Next, a buffer pattern 152 is formed on the first electrode150. The buffer pattern 152 is disposed at a boundary portion of thepixel regions P to cover and overlap edge portions of the firstelectrode 150. Next, a plurality of spacers each having a bar shape maybe formed on the buffer pattern 152 based on a subsequent step offorming an organic luminescent layer 155. Next, the organic luminescentlayer 155 is formed on the first electrode in the pixel region P. Theorganic luminescent layer 155 may be formed through one of a nozzlecoating method, an inkjet method, and a thermal evaporation method usinga shadow mask. Next, a second electrode 160 is formed on the organicluminescent layer 155. The second electrode 160 may be disposed as asingle body in a whole display area DA (of FIG. 4).

After the first and second substrates 110 and 170 are fabricated, thefirst and second substrates 110 and 170 are disposed to face each other.Next, a seal pattern 190 is formed between the first and secondsubstrates 110 and 170 corresponding to the first region A1, and thefirst and second substrates 110 and 170 are attached such that theorganic electroluminescent diode E (of FIG. 4) of the first substrate110 faces the first surface of the second substrate 170, thereby anorganic electroluminescent display device completed. For example, thefirst and second substrates may be attached in an environment such as aninert gas ambient and a vacuum.

In an organic ELD device, the light may be emitted upwardly and theorganic ELD device may have a top emission type since an absorbentmaterial is disposed at a non-display area. In addition, deteriorationof the substrate for encapsulation such as a break or crack of thesubstrate for encapsulation is prevented since a plurality of grooveshaving the absorbent material are formed in a boundary portion of asubstrate for encapsulation and a central portion of the substrate forencapsulation is thicker than the boundary portion. Further,deterioration of the organic ELD device due to bending of the substratefor encapsulation, such as the breakage of the second electrode of theorganic electroluminescent diode and electric shortage of the first andsecond electrodes the organic electroluminescent diode, is preventedsince a protection layer is formed on the substrate for encapsulation.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the organicelectroluminescent display device and the method of fabricating the sameof the present invention without departing from the sprit or scope ofthe invention. Thus, it is intended that the present invention coversthe modifications and variations of this invention provided they comewithin the scope of the appended claims and their equivalents.

1. A method for fabricating an organic electroluminescent display devicecomprising the steps of: preparing first and second substrates; formingan organic electroluminescent display on the first substrate; forming afirst etching mask film on an upper surface of the second substrate;forming a second etching mask film on a lower surface of the secondsubstrate; performing a first etching process on the upper surface ofthe second substrate; forming a third etching mask film on an etchedportion of the second surface of the glass substrate; performing asecond etching process on the upper surface of the second substrate toform a plurality of grooves on the upper surface of the secondsubstrate; removing the first and second etching mask films, the secondetching film remaining on the etched portion of the second surface ofthe glass substrate; and encapsulating the organic electroluminescentdisplay between the first and second substrates.
 2. The method forfabricating an organic electroluminescent display device according toclaim 1 further comprising the step of forming an absorbent material ineach of the plurality of grooves.
 3. The method for fabricating anorganic electroluminescent display device according to claim 1 whereinthe second etching mask is formed on the entire lower surface of theglass substrate.
 4. The method for fabricating an organicelectroluminescent display device according to claim 1 wherein thesecond etching film covers any protrusions formed on the upper surfaceof the second substrate.
 5. A method for fabricating an organicelectroluminescent display device comprising the steps of: preparingfirst and second substrates; forming an organic electroluminescentdisplay on the first substrate; forming a first etching mask film on anupper surface of the second substrate; forming a second etching maskfilm on a lower surface of the second substrate; performing a firstetching process on the upper surface of the second substrate; forming athird etching mask film on an etched portion of the second surface ofthe glass substrate; performing a second etching process on the uppersurface of the second substrate to form a plurality of grooves on theupper surface of the second substrate; removing the first, second, andthird etching mask films; forming a first insulating material layer onthe entire upper surface of the second substrate; removing end portionsof the first insulating layer, the first insulating layer remaining onthe etched portion of the second surface of the glass substrate; andencapsulating the organic electroluminescent display between the firstand second substrates.
 6. The method for fabricating an organicelectroluminescent display device according to claim 5 furthercomprising the step of forming an absorbent material in each of theplurality of grooves.
 7. The method for fabricating an organicelectroluminescent display device according to claim 5 wherein thesecond etching mask is formed on the entire lower surface of the glasssubstrate.
 8. The method for fabricating an organic electroluminescentdisplay device according to claim 5 wherein the first insulating layercovers any protrusions formed on the upper surface of the secondsubstrate.
 9. The method for fabricating an organic electroluminescentdisplay device according to claim 5 further comprising the step offorming a protection pattern on the first insulating layer.
 10. A methodof fabricating an organic electroluminescent display device, comprisingthe steps of: forming an organic electroluminescent diode on a firstsubstrate including a display area and a non-display area surroundingthe display area; forming a first etching mask film on first and secondsurfaces of a second substrate including a first region corresponding tothe non-display area, a second region corresponding to the display areaand a third region between the first and second region, the firstetching mask film disposed in the first region of the first surface andin the first, second and third regions of the second surface; etchingthe second substrate using the first etching mask film as an etchingmask so that the second substrate of the first region has a firstthickness and the second substrate of the second and third regions has asecond thickness smaller than the first thickness; forming a secondetching mask film on the first surface, the second etching mask filmdisposed in the second region of the first surface and in portions ofthe third region of the first surface, and other portions of the thirdregion of the first surface exposed through the second etching maskfilm; etching the second substrate using the first and second etchingmask films to form a plurality of grooves corresponding to the otherportions of the third region, the second substrate corresponding to theplurality of grooves having a third thickness smaller than the secondthickness; removing the first etching mask film on the first and secondsurfaces; forming an absorbent material in the plurality of grooves; andattaching the first and second substrates such that the organicelectroluminescent diode faces the first surface.
 11. An organicelectroluminescent display device comprising: a first substrateincluding a display area and a non-display area surrounding the displayarea; an organic electroluminescent diode in the display area on thefirst substrate; a second substrate facing and spaced apart from thefirst substrate, the second substrate including a first regioncorresponding to the non-display area, a second region corresponding tothe display area and a third region between the first and second region,wherein the second substrate includes a plurality of grooves in thethird region, and wherein the second substrate has a first thickness inthe first region, a second thickness smaller than the first thickness inthe second region and a third thickness smaller than the secondthickness in a portion of the third region where the plurality ofgrooves are formed; a protection layer in the second region on thesecond substrate; and a seal pattern in the first region between thefirst and second substrates.
 12. The organic electroluminescent displaydevice according to claim 11 further comprising an absorbent material ineach of the plurality of grooves.
 13. The organic electroluminescentdisplay device according to claim 11 further comprising a plurality ofprotection patterns.
 14. The organic electroluminescent display deviceaccording to claim 11 wherein the protection layer is on an innersurface of the second substrate.
 15. The organic electroluminescentdisplay device according to claim 11 wherein the protection layer has athickness between 2 μm and 3 μm.
 16. The organic electroluminescentdisplay device according to claim 11 wherein each of the plurality ofprotection patterns has a thickness between 1 μm and 2 μm.
 17. Theorganic electroluminescent display device according to claim 11 whereinthe protection layer includes one of acryl, polycarbonate, andpoly-ethylene-terephthalate.